The description of an experimental setup is presented, which allows the generation of high-frequency and microwave discharges for creating plasma streams in a wide range of operating parameters. Experiments on the generation of these discharges are described. Numerical modeling of the spatial distribution of electromagnetic fields that ensure the discharge sustainment under conditions corresponding to the actual parameters of the existing design and setup has been performed. Calculations of the absorption coefficients for waves at working frequency made it possible to determine the localization of absorption regions of the discharge and estimate the efficiency of the power introduced into the discharge for given discharge initiation techniques. The plasma parameters (the electron temperature and concentration) were obtained experimentally, and their dependences on the initial values of the pressure and power of electromagnetic field deposited into the discharge are presented. In the region of the placement of biopolymer samples, the parameters of the ion component of the plasma flow were determined. The results of the pilot studies on the influence of plasma on the physical and chemical properties of biopolymer samples are presented.
A compact time-of-flight neutron spectrometer was developed to study the production of neutrons at large angles in the energy range of 1–200 MeV. This spectrometer is a part of the BM@N facility at the extracted heavy ion beam of the Nuclotron accelerator at JINR. Stilbene-based detectors with silicon photomultipliers are used for the neutron registration. The main features of the spectrometer are high time resolution, short flight path, complete suppression of gamma-ray background using pulse shape discrimination, operation in a strong magnetic field, and event-by-event recording of digital data. The spectrometer’s characteristics were studied in an experiment with a beam of xenon nuclei at the energy of 3.8 A GeV.
The design of the MEPhIST-0 tokamak microwave interferometer and its system of data acquisition and processing are described. Examples of the time evolution of the linear electron density in MEPhIST-0 discharges are presented. The use of a phasemeter based on AD8302 detectors and digital post-processing of interferometer signals is compared. The beam refraction in the MEPhIST-0 chamber has been calculated. The possibility of plasma probing with a microwave interferometer for single- and two-pass configurations has been evaluated. It is shown that the transition to single-pass plasma probing allows the upper limit of the measured density to be significantly expanded (up to n0 = 3 × 1019 m−3).
In magnetic confinement nuclear fusion research, precise measurement of plasma radiative power is fundamental to understanding energy balance, physics of transportation, and ensuring safe device operation. This paper presentsmulti-channel integrated electronics, featuring an FPGA as the main controller and GbE communication, designed for metal foil detector with both positive and negative response channels for bolometer diagnostic. In this electronics design, compared to the single-channel electronics prototype developed recently, the phase shift circuit is optimized, DDS is adopted to generate carrier reference signal, and dynamic range compensation circuitry is incorporated. Within the constrained chassis, it integrates eight channels, significantly enhancing channel integration compared to the original BOLOMETER electronics on EAST. Performance testing in the electronics laboratory verified that all channels of this multi-channel integrated electronics exhibit consistent carrier excitation frequencies, with thethe maximum relative amplitude error of 0.48
The article presents a dual-band S + X receiving system for a mobile VLBI station. The input frequency range is 2.2–2.6 GHz in the S-band and 8.2–9.1 GHz in the X-band. The receiving system output frequency range is 0.1–1 GHz. The paper presents the receiving system’s functional diagram and the cryogenic receiving focal unit (CRFU) layout. CRFU structure and operating principle are considered. The calculated and measured characteristics of the receiving system and CRFU are presented. The control, power-supply, and telemetry system structure, composition, and operating principle are discussed.
A digital filter for trapezoidal pulse shaping of exponential doublets has been implemented in a field programmable gate array (FPGA). These signals are typical of particle detectors, and the shaping is necessary to avoid pileup of smoothly decaying pulses in order to precisely measure their relative amplitudes. It was found out that, in single-board ADC-SoC computer combining an analog-to-digital converter (ADC) and an FPGA, the input ADC circuit adds the third time constant to exponential doublets, thereby distorting them. So, the digital filter has been analytically calculated and implemented in the FPGA for the trapezoidal shaping of pulses that we call the exponential triplets. The conditions for the stability of this filter have been determined. The amplitude spectrum of artificial exponential doublets has been measured.
The results of calibration of a multicathode proportional counter designed for recording single-electron events in experiments to search for hidden photons of dark matter are presented. Two operating modes of the counter were investigated: the classical single-avalanche mode described by the Polya distribution, and the multiavalanche mode with the Poisson distribution. It has been shown that the application of fresh polyurethane varnish to the internal surfaces followed by immediate pumping leads to an increase in the pulse amplitude by two orders of magnitude and a transition to a multiavalanche regime. The effect disappears only after prolonged contact of the varnish with air and subsequent pumping out. Both modes are used in experimental practice to improve detection reliability.
An approach to modifying the configuration of an optical frequency reflectometer by replacing two special service channels, including an auxiliary interferometer and a gas cell, with a single channel is described. In this configuration, the sensory characteristics of the system were studied. Digital filtering methods were used to extract useful information. It is shown that the presented method allows to avoid the use of an extra channel of the analog-to-digital converter and photodetector, while the reflectogram and correlation functions are restored by the equal-frequency resampling algorithm without loss of information.
A method is presented for measuring and analyzing the parameters of charged microparticles (micrometeorites) in the velocity range of 0.5–10 km/s and the range of electric charges from 1 fC to 1 pC. The method is based on a five-electrode grid time-of-flight detector with a 10-mm pitch and a 1-mm cell. A nonstandard approach to signal digitization has been developed. An SDRplay RSP1 software-defined radio (SDR) receiver operating in direct conversion mode at a minimum frequency with the capture bandwidth of 8 MHz is used as a wideband analog-to-digital converter. Processing of digitized data, including bandpass filtering, envelope detection, threshold event selection, and pulse parameter analysis, is implemented in the GNU Radio environment. The particle velocity and electric charge are determined from the time interval between pulses and their amplitude, respectively. It has been experimentally confirmed that the proposed SDR-based hardware and software provide flexibility and reduce the cost of the measuring system, keeping its metrological characteristics sufficient for the stated measurement ranges.
A microprocessor-based temperature-compensated bias voltage source is presented. It stabilizes the gain of a silicon photomultiplier (SiPM) within the temperature range of 10–60°C. The temperature dependence is compensated via dynamic correction of the bias voltage according to the measured temperature and individual parameters of a particular photomultiplier. Experimental studies were performed on two PM3325-WB-D0 SiPM specimens and confirmed the efficiency of the proposed approach: the gain spread does not exceed ±1.5
The paper proposes a new approach to the design of measuring circuits for monitoring the progress of the radio-wave surgery operations, in which the testing-effect loop is excluded from the measurement process, and monitoring is carried out by analyzing the characteristics of the oscillator signal that sets the active influence. The paper describes a method for assessing and tracking the state of the biological tissue using a directional coupler. A design and a scheme for integrating such a transducer in a surgical device have been developed. The functionality of the proposed device has been mathematically simulated and experimentally verified. It has been proven and demonstrated that monitoring the dynamic active impedance allows tracking the effects of electromagnetic radiation on the structural changes in biological tissues. This proposed method of real-time monitoring enhances the efficiency and safety of high-frequency electrosurgery.
A Solntse–Terahertz space experiment is scheduled for implementing aboard the Russian segment of the International Space Station starting in 2026. The objectives of the experiment are to obtain data on the terahertz radiation of the Sun and to study solar active regions and solar flares in the 0.4–12.0-THz range. This work presents preliminary experimental results on measuring solar radiation in the 8–14-μm atmospheric transparency window ( 20–40 THz) using a ground-based setup equipped with a detector analogous to those employed in the “Solntse-Terahertz” scientific instrumentation.
A prototype plasma rocket thruster based on a quasi-stationary high-current plasma accelerator (QSPA) is being developed at JSC SRC RF TRINITI. According to the technical specifications, the accelerator must operate in a pulse-periodic mode with a frequency of 10 Hz. It is necessary to register the plasma flow velocity at each launch, because it is an important characteristic of accelerator operation. An algorithm for automated processing of time-of-flight diagnostics of plasma flow velocity, a traditional approach at QSPA, has been developed. The proposed algorithm allows for determining the time dependence of the delay time between signals during a discharge pulse. The estimated error in the calculation results is less than 30
A nanosecond microwave pulse source based on a nonlinear transmission line (NLTL) with saturated ferrite, operating in the S-band, has been developed and experimentally tested. Its key feature is the absence of electromagnets in its design. The source consists of a sharpening NLTL with an unsaturated ferrite, a corrugated NLTL, a coaxial high-pass filter, and a combined antenna. Both the sharpening and corrugated lines utilize NiZn ferrite rings. NdFeB permanent magnets are used to saturate the ferrite in the corrugated NLTL. The line provides efficient generation of high-frequency pulses in the frequency range of 2.7–3.6 GHz. The operating voltage range of the source is 50–190 kV. The coaxial high-pass filter has a passband of 1.2–4 GHz, which allows for effective radiation of oscillations excited in the line as well as the high-frequency energy concentrated on the front of the voltage pulse. The combined antenna has an operating range of 1–4 GHz. A pulsed periodic operating mode was implemented with a pulse repetition rate of 50 Hz up to 2000 pulses per burst. At an operating voltage of 170 kV, the central frequency of the radiated pulse is 3.4 GHz. The effective potential of the source is 65 kV.
A new method for constructing a measurement system for interrogating fiber-optic interferometric sensors has been experimentally demonstrated. This method is based on a software-defined radio receiver (SDR, Analog Devices PlutoSDR plus). The object of investigation is a Mach−Zehnder interferometer subjected to acoustical action from a low-power dynamic head and a step motor. A key feature of the proposed approach is to use a single SDR device in two functions: as a generator of an RF modulating signal for a laser source and as a receiver/demodulator for the photodetector signal of the interferometer. The fundamental applicability of the method for recording acoustic vibrations by receiving and processing the RF signal has been experimentally shown.
A system for improving the uniformity of ion-beam treatment of substrate surfaces and minimizing coating thickness inhomogeneity during magnetron sputtering has been proposed. A system for varying the ion incidence angle and substrate positioning has been tested, demonstrating a ninefold increase in the ion-beam treatment area and an increase in thickness uniformity during magnetron sputtering of up to 90
The main requirements for a new mobile radio telescope for very-long-baseline radio interferometry (VLBI) have been formulated. Several options for implementing the antenna system of a radio telescope are presented. The basic operating principles and design features of dual-band and wideband receiving systems for a mobile VLBI station are considered. The calculated characteristics of the receiving system and the new radio telescope of the mobile VLBI station are presented.
Attention is drawn to the effect of the self-field HHT of bias current IHT through a Hall transducer (HT) on the objects of study and the measurement accuracy of the Hall magnetometer. The field HHT of the n-InSb-i-GaAs heteroepitaxial HT is considered. It is found that the force lines of the induction of HHT undergo a stepwise change in their direction at the edges of a thin epitaxial n-InSb film. In the case of nonuniform distribution of IHT over the cross section of the film, these jumps create a voltage across the Hall contacts due to the anisotropy, growth-induced defects, and nonequipotentiality of the Hall contacts, thus, leading to the measurement error. Exact compensation of HHT by the field of a current in antiphase to IHT makes it possible not only to eliminate the effect of the self-field on the objects of study but also to lower the detection threshold of the magnetometer from approximately 2.5 × 10–7 to approximately 5.75 × 10–9 T in the range of fields from 2.5 × 10–9 to 5 × 10–7 T and temperatures from 77.4 to 150 K.
The design of a miniature flow helium cryostat intended for Mössbauer, X-ray diffraction, and optical studies of samples in the temperature range of 4.2–300 K is described. The cryostat’s miniature size allows for maximum compatibility with other devices, such as Mössbauer spectrometers, magnets, and optical systems. On the other hand, the low mass of the “cold finger” on which the sample is placed reduces the consumption of helium required to maintain the cryostat’s operating temperature. This also makes it less inert, i.e., it speeds up the transition from one temperature to another.
The design of an installation that allows conducting experiments to test the theory of interaction of two charged bodies is presented. A description of individual design elements and their main technical characteristics is provided. The results of testing this installation and their comparison with calculations are given. This design is used as a training laboratory setup and can also be used as a prototype for electrical separation of solid mixtures or electrical cleaning of gases. This laboratory work can be completed remotely.
